1. Field of the Invention
The invention relates to air entry passages such as are used in several types of engines and as are particularly useful in direct injection diesel engines. Such passages are also useful in stratified charge engines.
2. Prior Art
Swirl type inlet passages for diesel engines fall generally into tangential types where the air is introduced tangentially into the cylinder bore through a somewhat straight passage and snail types wherein the air is preswirled within the passage itself which is shaped somewhat like the shell of a snail and in addition is introduced tangentially to the cylinder bore. Through use of the snail type passages one might hope to obtain a better swirl of the air as it is introduced into the cylinder bore. However, such snail type passages are relatively inefficient since there is considerable loss of energy as the air is directed therethrough. On the other hand, the prior art somewhat straight passages which introduce air tangentially into the cylinder bore have not produced sufficient swirl. A tangential type straight passage which would accomplish adequate swirl but with only minimum energy losses would thus be highly desirable. Also, such a design could be expected to take up less valuable space about the engine than do the snail type air entry passages.